Depends on several factors. Assuming Nazis were defeated and Soviet influence didn't extend beyond Hungary, we would have likely become a proxy zone for NATO. Most likely a large portion of Marshall plan money would be have been set aside for regional development, not unlike what happened with Greece. Urbanisation would probably be at a greater pace with a highly sped up ruination of peasantry. No idea if Yugoslavia would even be a thing as such since communist ideology played a significant role in glueing its nations together. Instead of planned development, you'd have high investments in key industries and towns while rest of the country would be left unattended. Historically wealthier countries like Slovenia and Croatia would probably be richer compared to today. Serbia and Bulgaria, similar to greece, would be in a middle zone (maybe slightly better in certain parts of the country, though overall probably worse), everyone else would probably be worse off than today across the board.

All of this is of course speculation, but an advantage that communism had over capitalism historically is to be able to industrialise quickly without breaking social cohesion. Capitalist development historically was usually slower (spanning hundred years) during which society undergoes severe turmoil due to ruination of peasantry and unregulated and unplanned urbanisation.

Those thinking that economically we'd be anywhere near most Western European countries highly underestimate the differences in development which would dictate the relationship balkan countries would have had with Western Europe. Capitalism tends to favour historically richer countries and those countries have an invested interest in maintaining this circumstance, why would they allow abotger regional competitor when they could be the only ones dictating the competition.